A typical automotive system includes an engine-driven air conditioning (AC) compressor. The AC compressor compresses refrigerant in an AC system in order to circulate the refrigerant in the system under pressure. To operate the AC compressor, an electromagnetic AC compressor clutch enables the transfer of torque generated by an energy conversion device, such as an engine, to the AC compressor.
When not in use, the AC compressor is de-clutched to reduce engine power draw and to prevent stressing the compressor related componentry. When in use, the AC compressor clutch is engaged. Besides the engine power consumed turning the compressor, this clutch engagement draws a significant amount of electrical power. Presently, a single voltage, typically vehicle voltage, is applied to the electromagnetic clutch to engage the clutch as well as to maintain the engagement.
Other attempts to address control of an AC compressor clutch include applying different electrical power levels to the compressor clutch. One example approach is shown by Major et al. in U.S. Pat. No. 8,332,098. Therein, an AC compressor voltage controller controls the electric power input to a compressor clutch that selectively drives an AC compressor in a vehicle AC system by determining a first electric power level needed to cause the compressor clutch to move to a full engagement position, applying the first electric power level to the compressor clutch to cause the compressor clutch to move to the full engagement position, determining a second electrical power level needed to maintain the compressor clutch in the full engagement position, and applying the second electrical power level to the compressor clutch to maintain the compressor clutch in the full engagement position.
However, the inventors herein have recognized potential issues with such systems. As one example, the second electrical power level applied to the compressor clutch may be more than sufficient for maintaining engagement of the compressor clutch, and so excess electrical power may be used. Conversely, the second electrical power level applied to the compressor clutch may not be sufficient for maintaining engagement of the compressor clutch. Furthermore, in some examples the second electrical power level applied to the compressor clutch may be initially sufficient for maintaining clutch engagement but later may be insufficient for maintaining clutch engagement.
In one example, the issues described above may be addressed by a method for a clutch of an air conditioning system in a vehicle, the method comprising monitoring a clutch of an air conditioning system in a vehicle when the air conditioning system is activated, and responsive to determining that the clutch is not engaged, increasing a current flow to the clutch. In this way, engagement of the compressor clutch may be dynamically maintained with a reduced usage of electrical power.
In another example, the issues described above may be addressed by a method for a clutch of an air conditioning system in a vehicle, the method comprising monitoring refrigerant pressure in the air conditioning system when the air conditioning system is activated, and adjusting voltage applied to a compressor clutch based on the refrigerant pressure. In this way, an operating condition such as refrigerant pressure may be used as feedback to control a compressor clutch. Furthermore, clutch position can be inferred without the use of a sensor dedicated to monitoring the clutch position.
In yet another example, a system comprises an energy conversion device configured to generate torque, a compressor configured to compress refrigerant, a compressor clutch coupled to the energy conversion device and configured to transfer torque from an energy conversion device to the compressor during engagement of the compressor clutch to the compressor, and a controller electrically coupled to the compressor clutch and configured with executable instructions stored in non-transitory memory that when executed cause the controller to: monitor engagement of the compressor clutch, and responsive to disengagement of the compressor clutch when the compressor clutch is commanded to engage, increase a current flow to the compressor clutch. In this way, a compressor clutch may consume an optimal amount of power, and any clutch slippage due to the reduced amount of power consumed by the compressor clutch can be promptly mitigated.
It should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure.